Detection of silica in a liquid (e.g., water) can use colorimetric techniques. For example, a silica-molybdate complex can be formed and measured by measuring absorption of probe light at a wavelength of 450 nm. Alternatively, a silica-molybdate-heteropoly blue complex can be formed and measured by measuring absorption of probe light at a wavelength of 810 nm. These and other colorimetric processes may require the addition of several chemical reagents in various steps with each step taking up a defined period of time to allow for sufficient mixing and reaction.